This invention relates to borescopes, endoscopes, or laparoscopes of the type in which a miniature video camera is mounted at a distal viewing head of an elongated insertion tube. The invention is more particularly concerned with an improved laparoscope improved to facilitate repair or replacement of the image-gathering optics.
Recently, the need and preference for less invasive surgical techniques has increased. Likewise, there is an increased interest in the use of video instruments for surgical applications. Video-based procedures have been proposed for minimal intervention in the patient. An example of a minimally invasive video instrument is a laparoscope for performing surgery in the abdominal cavity, where the instrument is inserted through a small incision. Other, narrow probes can be used in eye surgery. Further examples are found in industrial probes, i.e., borescopes for inspection of equipment such as boilers or steam generators, or jet engine rotors where non-destructive penetration of the equipment is necessary.
Traditional optical laparoscopes require an elongated lens tube which employs an objective lens at the distal end an ocular or eyepiece at the proximal end, and a complex series of relay lenses to carry the visual image from the objective to the ocular. For laparoscope of modest to large size, discrete lenses are used for the relay lenses. For very small diameter probes, rod lenses can be used. In either case, the relay lenses are both high-cost items, and at the same time quite delicate. For example, if the lens tube is dropped or struck, some portion of the lens system can easily shatter. If this happens, the lens tube must be replaced, at a cost of several thousands of dollars. Consequently, the industry has sought ways to reduce the risk of breakage, either by making the laparoscope more rugged or by reducing the costs of repair or replacement. However, this goal has been elusive with traditional optical scopes.
A video laparoscope with a light source based on a small, low-power metal halide discharge lamp is described in copending patent application Ser. No. 07/780,762, filed Oct. 22, 1991, and having a common assignee. As described in that patent application, a laparoscope or other similar probe has a miniature video camera that incorporates a miniature electronic imager and a lens assembly which are disposed either at the distal tip or at a proximal end of a insertion tube. For insertion tubes of about 5 mm or larger, the camera can be distally mounted. For very slim insertion tube, the camera can be proximally mounted, with a relay lens system being contained in the insertion tube. The insertion tube can be rigid or can have its tip portion articulatable. The small video camera can be incorporated in an add-on camera attachment for laparoscope having a proximal viewing port.
Disposing the camera at the distal tip of the insertion tube reduces the amount of focussing and relay lenses to be carried in the tube. This reduces the vulnerability of the lens system and also means less light is lost in the lens system. The amount of optical fiber bundle needed for illumination is reduced, which also permits the insertion tube to be made narrower.
The insertion tube proximal end is coupled through a flexible cable or umbilical to a connector module that plugs into a socket in a processor unit. A video cable that extends through the insertion tube and umbilical has terminals in the connector module that supply the video signal from the miniature camera signal to a full color or monochrome monitor. An image of a target area, such as a tissue within a patient's body cavity, can be viewed on the monitor.
Also within the processor is a high illuminance, but low-wattage light source in the form of one or more metal halide discharge lamps. These can preferably be of the type described in copending U.S. patent application Ser. Nos. 07/484,166, filed Feb. 23, 1990; 07/636,743, 07/636,744, each filed Dec. 31, 1990, and which have an assignee in common herewith. The lamp typically operates at a power of about 20 watts, and has an efficacy of at least 35 lumens per watt. The light produced, which can be controlled by the selection of salts employed, the dosage of mercury, and mechanical structure of the lamps, has an emission spectrum in the visible band, with very little radiation produced in the infrared band. Also, the arc gap of this lamp is small, which produces a small spot of light when focused onto the fiber optic bundle used for illumination. The small spot size allows all the light energy to be directed into the proximal end of a very small fiber bundle.